Gear pump

ABSTRACT

A gear pump or a gear motor has a housing of synthetic plastic material, an interior chamber of which there is mounted a pair of meshing gears. The gears are each mounted on a rotating shaft having journalling pins at opposite ends and these pins are journalled in cup-shaped metallic journalling sleeves whose open ends face the interior of the chamber and are bounded by radial flanges, and whose closed ends are closed by a transversely extending wall which is at least in part exposed to the ambient atmosphere at the exterior of the housing.

United States Patent 1191 1111 3,859,014

Dworak et al. Jan. 7, 1975 GEAR PUMP 2,519,588 8/1950 McCulloch 1. 418/178 1 2,966,860 1/1961 Maynard 418/152 [75] lnvenwrs- Wllhelm F F" 3,128,710 4/1964 Blomgren et a1. 418/152 x Wolfgang T911110, 0981161911 both Of 3,294,028 12/1966 Dflhl 418/135 x Germany 3,390,638 7/1968 Adams 418/206 X Assigneez Robert Bosch Gum-Ln. Stuttgart, 3,433,168 3/1969 Banker .1 418/206 X Germany Primary Examiner-William L. Freeh [22] Filed: June 29, 1972 Assistant ExaminerRichard E. Gluck [2]] Appl NOJ 267,710 Attorney, Agent, or FirmMichael S. Striker [57] ABSTRACT 1 1 Foreign Application Priority Data A gear pump or a gear motor has a housing of syn- July 20, 1971 Germany 2136214 thetic plastic material, an interior chamber of which there is mounted a pair of meshing gears. The gears [52] U.S. Cl 418/135, 418/152, 418/178, are each mounted on a rotating shaft having journal- 418/179, 418/206 ling pins at opposite ends and these pins are journalled [51] Int. Cl F01c 19/08, F01c 21/00 in cup-shaped metallic journalling sleeves whose open [58] Field of Search 418/178, 135, 206, 152, ends face the interior of the chamber and are bounded 418/179 by radial flanges, and whose closed ends are closed by a transversely extending wall which is at least in part [56] References Cited exposed to the ambient atmosphere at the exterior of UNITED STATES PATENTS the housmg- 2,202,913 6/1940 Johnson 418/178 8 Claims, 2 Drawing Figures y/ y 6 a 1 7 77 l 78 Z2 Z2 PA 1 75 1 1 l4 8 1 75 l 1 1 l l l l GEAR PUMP BACKGROUND OF THE INVENTION The present invention relates to a hydrostatic apparatus in general and more particularly to a gear pump or gear motor.

It is already known to provide gear pumps or gear motors with housing of synthetic plastic material. In fact, a prior art teaching provides for a synthetic plastic housing of two parts which are assembled together and in the interior of which there are mounted two meshing gears which are also of synthetic plastic material. These gears have an annulus of teeth which is much wider than the respective hub and the driving gear is mounted on a metal shaft which extends out of the housing and is journalled in a sleeve. The interior chamber of the housing is sealed against escape of fluid by a shaft seal which is mounted on the shaft on which the driving gear is provided. The driven gear has a very narrow hub and is journalled in the housing without the use of a shaft.

In this gear construction the various components of synthetic plastic material are in direct frictional contact. Needless to say this results in the development of frictional heat, but this prior art construction makes no provision for removing such heat, which can be at most unsatisfactorily dissipated. Experience has shown that the only way in which destruction of this prior-art hydrostatic apparatus due to friction-created heat can be avoided is by producing the various components of the apparatus with rather large tolerances, so as to have significant play in operation. This reduces the amount of frictional heat created and avoids the destruction of the device due to the development of such heat. Concomitantly, however, it prevents the device from operating with any but very low degree of efficiency, and when it is used as a pump it cannot produce any high pump pressures. Added to these drawbacks is the fact that the construction of the housing from two parts requires the use of special sealing means in order to properly seal the chamber of the housing with respect to the interior.

SUMMARY OF THE INVENTION hydrostatic apparatus which is capable of providing high pressures and of operating with great efficiency.

In pursuance of these objects and of others which will become apparent hereafter, one feature of the invention resides in a gear pump or gear motor which, briefly stated, comprises a housing of synthetic plastic material having an internal chamber. A pair of meshing gears are provided in this chamber and they each include a mounting shaft having journalling pins at its opposite ends. A plurality of cupped metallic journalling sleeves journal the respective journalling pins for rotation. Each of these sleeves has an open side facing into the chamber and a closed side provided with a transverse wall which is exposed at least in part exteriorly of the housing to the ambient atmosphere.

The apparatus according to the present invention assures, due to the provision of the above-mentioned journalling sleeves and their at least partly exposed transverse end walls, that any frictional heat resulting during operation is conducted directly to the exterior of the housing by the metallic journalling sleeves which are good thermal conductors. This means that any build up of heat to levels which could cause damage to the apparatus such as uncontrolled deformations of the components of the apparatus is reliably avoided, and avoided in a simple manner.

The invention also proposes to mount on that journalling sleeve through which an end portion of the shaft for the driven or driving gear is journalled, a cupshaped of pot-shaped mount for a shaft seal with such mount having a transverse wall through which the shaft extends to the exterior of the housing, and with the circumferential wall of the mount being at least in part exposed (i.e. being uncovered by the plastic material of the housing) to the ambient atmosphere.

The journalling sleeves are advantageously provided with radial-flanges surrounding the region of their open ends and clamp-shaped springs engage the exterior of the sleeves and maintain the flanges in sealing contact with the axial end faces of the gears.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an axial section through an apparatus according to the present invention; and

FIG. 2 is an end view of the apparatus in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing the drawing in detail, it will be seen that reference numeral 1 identifies the housing of the novel hydrostatic apparatus that is the gear pump or gear motor, which housing is of synthetic plastic material and is of one-piece being produced in a single operation.

The housing 1 has an internal chamber composed of two overlapping portions 2, 3 in which there are mounted two gears 4, 5 which mesh with one another. The gears are mounted on shafts l0 and 11, respectively, and the latter in turn are journalled in metallic journalling sleeves 6, 7, 8 and 9.

As the drawing shows the journalling sleeves 6, 7 and 8 are cupped, and have outer closed ends provided with transverse end walls 12, 13 and 14. These end walls l2-l4 are so located that in the illustrated embodiment they form a part of the outer surface of the housing I; in other words, the end walls 1244 are exposed to the ambient atmosphere exteriorly of the housing and are not covered by the plastic material of the latter. in accordance with the invention it is essential that if not completely uncovered, the ends walls 12-14 are at least in part uncovered by the plastic material and exposed to the ambient atmosphere.

The additional journalling sleeve 9 is provided with a journalling bore and through the sleeve 9 the shaft 10 extends out of the housing 1, the shaft 10 serving either for input or output purposes, that is its associated gear being either driven by the shaft 10 or driven via the other gear. At the end of the sleeve 9 facing away from the interior chamber of the housing, there is provided a cup-shaped mount for a shaft seal 16 which seals the shaft 10 with respect to the chamber of the housing to prevent the escape of fluid from the latter. The cylindrical portion of the mount 15 extends out of the housing 1.

Flanges l7, 18, 19 and 20 are provided on the sleeves 6 9, respectively at the inner ends thereof which face the interior of the chamber. These flanges 17-20 engage the respectively adjacent axial end faces of the gears 4 and 5 and define the interior space of the chamber, together with a cylindrical insert 21 of metallic sheet material strip which is formed to correspond to the contour of the inner cylindrical surface of the chamber. The width of the strip of which the insert 21 is composed corresponds to the width of the gears 4 and 5 except for a small amount of play.

Springs 22 of clamp-shaped configuration are embedded in the plastic material of the housing 1 and contact the outer sides of the flanges 17-20 urging them in at least substantially sealing contact with the respective axial end faces of the gears 4 and 5.

' Two tubular sections are embedded in the material of the housing 1, constituting an inlet 23 and an outlet 24 for the fluid which is to pass through the apparatus. The tubular portions extend outwardly beyond the housing 1 by the extent necessary to permit connection to them of the fluid conduits supplying and removing the fluid. Two mounting lugs 25 and 26 are formed at the outside of the housing so that the latter can be mounted wherever necessary.

The operation of the apparatus disclosed herein is so well known that it requires no detailed discussion. However, the present invention is concerned not only with the apparatus per se, but also with the method of making it. It is therefore pointed out that to make the novel apparatus the sleeves 6-9 are pushed onto the shafts l0 and 11 on which the gears 4 and 5 are already mounted. The insert 21 is then placed around the shafts and gears and springs 22 are pushed onto this assembly to hold it together. The thus completed assembly is introduced into a mold and a hardenable synthetic plastic material is cast about it to form the housing 1 which is unitary and which tightly and securely surrounds the chamber and holds all components in place.

It is, however, also within the intent of the present invention to produce the housing by injection molding rather than by casting. If the mold is appropriately produced, with a view towards holding the various components in place, then the springs 22 can be omitted.

The sleeves 6 9 are advantageously, but not necessarily made of aluminum. This has the advantage that they can be produced in a simple and inexpensive deformation operation, for instance by flow-pressing. Moreover, aluminum has a high coefficient of thermal conductivity and has been found to be excellently suited as the material for the journal sleeves 6 9. (Plastic material suitable for making the housing 1 could be e. g. polyester resin, epoxy resin or silicon resin.)

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of construction differing from the types described above.

While the invention has been illustrated and described as embodied in a hydrostatic apparatus, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

We claim:

1. A gear pump or gear motor comprising a housing of synthetic plastic material having an internal chamber and an inlet and an outlet communicating with said chamber, a pair of meshing gears having opposite end faces provided in said chamber and each including a mounting shaft having journalling pins at its opposite ends; a plurality of cupped metallic journalling sleeves journalling the respective journalling pins for rotation, each of said sleeves having an open side facing into said chamber, a closed side providedwith a transverse wall extending at least in part exteriorly of said housing and exposed to the ambient atmosphere, and a transverse flange in engagement with said respective end faces of said gears so as to conduct heat from said gears via said transverse wall to the exterior of said housing; spring clamps having intermediate and transversely extending end portions embedded in the material of said housing, and said transversely extending end portions engaging said flanges at the sides thereof facing away from the respective end faces of said gears for pressing said flanges against said end faces.

2. A gear pump or gear motor as defined in claim 1, said chamber being in part bounded by a substantially cylindrical surface; and wherein said sleeves have respective flanges each encircling one of said open sides and bounding said chamber together with said substantially cylindrical surface.

3. A gear pump or gear motor as defined in claim 2, said gears having respective axial end faces; and wherein said flanges are in engagement with respective ones of said end faces.

4. A gear pump or gear motor as defined in claim 2; further comprising a substantially cylindrical metalstrip insert accommodated in said chamber and overlying said cylindrical surface; said insert having a length corresponding substantially to that of the respective gears.

5. A gear pump or gear motor as defined in claim 1, one of said shafts having a shaft portion extending to the exterior of said housing; and further comprising a cupped metallic retainer accommodating a shaft seal, said retainer having a transverse wall through which said shaft portion extends, and a circumferential wall which is at least in part exposed to the ambient atmosphere.

6. A gear pump or gear motor as defined in claim 1, wherein said inlet and outlet are at least in part constituted by tubular elements extending to the exterior of and projecting beyond said housing.

7. A gear pump or gear motor as defined in claim 1, wherein said sleeves are of aluminum.

8. A gear pump or gear motor comprising an integral housing of plastic material having an internal chamber and an inlet and an outlet communicating with said chamber; a pair of meshing gears in said chamber and having opposite end faces and each including a mount ing shaft having journalling pins projecting outwardly from the respective end faces, one of said journalling pins projecting beyond the outer surface of said housing and the other of said journalling pins ending short of said outer surface; a plurality of metallic journalling sleeves journalling the respective journalling pins and each having an open side at the respective end face, and each of said sleeves for said other of said journalling pins having a side formed by a transverse wall at the outer surface of said housing and exposed to the ambient atmosphere to thereby dissipate heat, each of said sleeves having a transverse flange in engagement with the respective end face of said gears; substantially U-shaped spring clamps embedded in the material of said housing and engaging said flanges at the sides thereof facing away from the respective end faces of said gears for pressing said flanges against said end faces; and a cup-shaped retainer accommodating a shaft seal and having a transverse wall at said outer surface likewise exposed to the ambient atmosphere and provided with an opening through which said one journal pin projects. 

1. A gear pump or gear motor comprising a housing of synthetic plastic material having an internal chamber and an inlet and an outlet communicating with said chamber, a pair of meshing gears having opposite end faces provided in said chamber and each including a mounting shaft having journalling pins at its opposite ends; a plurality of cupped metallic journalling sleeves journalling the respective journalling pins for rotation, each of said sleeves having an open side facing into said chamber, a closed side provided with a transverse wall extending at least in part exteriorly of said housing and exposed to the ambient atmosphere, and a transverse flange in engagement with said respective end faces of said gears so as to conduct heat from said gears via said transverse wall to the exterior of said housing; spring clamps having intermediate and transversely extending end portions embedded in the material of said housing, and said transversely extending end portions engaging said flanges at the sides thereof facing away from the respective end faces of said gears for pressing said flanges against said end faces.
 2. A gear pump or gear motor as defined in claim 1, said chamber being in part bounded by a substantially cylindrical surface; and wherein said sleeves have respective flanges each encircling one of said open sides and bounding said chamber together with said substantially cylindrical surface.
 3. A gear pump or gear motor as defined in claim 2, said gears having respective axial end faces; and wherein said flanges are in engagement with respective ones of said end faces.
 4. A gear pump or gear motor as defined in claim 2; further comprising a substantially cylindrical metal-strip insert accommodated in said chamber and overlying said cylindrical surface; said insert having a length corresponding substantially to that of the respective gears.
 5. A gear pump or gear motor as defined in claim 1, one of said shafts having a shaft portion extending to the exterior of said housing; and further comprising a cupped metallic retainer accommodating a shaft seal, said retainer having a transverse wall through which said shaft portion extends, and a circumferential wall which is at least in part exposed to the ambient atmosphere.
 6. A gear pump or gear motor as defined in claim 1, wherein said inlet and outlet are at least in part constituted by tubular elements extending to the exterior of and projecting beyond said housing.
 7. A gear pump or gear motor as defined in claim 1, wherein said sleeves are of aluminum.
 8. A gear pump or gear motor comprising an integral housing of plastic material having an internal chamber and an inlet and an outlet communicating with said chamber; a pair of meshing gears in said chamber and having opposite end faces and each including a mounting shaft having journalling pins projecting outwardly from the respective end faces, one of said journalling pins projecting beyond the outer surface of said housing and the other of said journalling pins ending short of said outer surface; a plurality of metallic journalling sleeves journalling the respective journalling pins and each having an open side at the respective end face, and each of said sleeves for said other of said journalling pins having a side formed by a transverse wall at the outer surface of said housing and exposed to the ambient atmosphere to thereby dissipate heat, each of said sleeves having a transverse flange in engagement with the respective end face of said gears; substantially U-shaped spring clamps embedded in the material of said housing and engaging said flanges at the sides thereof facing away from the respective end faces of said gears for pRessing said flanges against said end faces; and a cup-shaped retainer accommodating a shaft seal and having a transverse wall at said outer surface likewise exposed to the ambient atmosphere and provided with an opening through which said one journal pin projects. 